Cal. Public Utilities Code § 11942

With the consent of the board, the treasurer may: (a) Authorize the trust department of any state or national bank, or a trust company authorized to act as such, to receive as his agent deposits of any securities acquired by the district. (b) Place and maintain for safekeeping as a trust deposit with the trust department of any state or national bank, or a trust company authorized to act as such, any securities owned by the district. The bank or trust company selected shall have a total paid-in capital of at least one million dollars ($1,000,000). The treasurer shall take from the trust department or trust company a receipt for the securities, and neither the treasurer nor the district is responsible for the custody and safe return of the securities until they are withdrawn from the trust department or trust company by the treasurer. Any trust department or trust company to which securities are delivered, either as agent or depositary for the treasurer, shall make such disposition of the securities as the treasurer directs and is responsible only for strict compliance with written instructions given to it by the treasurer. All such securities are at all times subject to the order of the treasurer.